Manufacture of lubricating oil



LUBRIQAT'ING on.

. 1 MIXER v 2.. SOLVENT v I 4 CHILLER I f I z CHILLER, 3 1 1o WASH FILTER I FILTRATE f5 m3; FILTRATE r L so H I CHIL ER WENT FILTER MIXER v I WENT STILL' SETTLER EXTRACT RAFFINATE PHASE PHASE 16-1 I 18 SOLVEN'I" STILL STILL SOLVENT EXTRACT RAFFINATE FRANCIS X.GOVERS INVENTOR HIS ATTORNEYS Patented Aug. 6, 1940 MANUFACTURE OF LUBRIC'ATING OIL Francis X. Govers, Vincennes, Ind., assignor to Indian Refining Company, Lawrenceville, 111., a

corporation of Maine Application March 29, 1932, Serial No. 601,888

23 Claims.

This invention relates to the manufacture of lubricating oil from hydrocarbon oils, and more particularly to the manufacture of high viscosity index, low pour test lubricating oil from wax-bearing mineral oils.

In its broadest aspect, the invention contemplates an improved process of treating hydrocarbon oils, particularly paraflin-bear'ing lubricating fractions of petroleum with solvents to selectively produce therefrom low pour test lubricating oils characterized by having a desired viscosity temperature relationship and improved lubricating qualities. The invention contemplates 'a process of manufacturing lubricating oils having a low pour and cloud test, low sulphur content, low Conradson carbon content, a relatively high viscosity index and free from bodies of little or no lubricating value.

Low pour test in a lubricating oil denotes an oil, as. used in internal combustion engines, possessing the characteristics of easy starting in cold weather and readiness of flow suflicient to respond to methods of circulation so as to immediately reach all parts necessary to be lubricated.

The presence of sulphur or sulphur-containing bodies in lubricating oil is objectionable on account of the corrosive eiiect of sulphur upon bearing surfaces and other metal portions of the engine. Efforts to reduce the sulphur content of lubricating fractions to a desirable degree by methods ordinarily employed have resulted in an over-refined oil with impaired lubricating value.

Lubricating oil having a low Conradson carbon content is desirable since such oil has little tendency to carbonize in the motor, and such carbon as may be deposited is of a flocculent nature,

having little or no tendency to adhere to the piston head or cylinder walls. High Conradson carbon content is characteristic, for example, of

oils have the property of possessing the desired viscosity at elevated temperature with no great loss of mobility at very low temperature.

Lubricating oi1s,1as ordinarily made from naphthene-base crudes, have a low pour and cloud test, low Conradson carbon content, but have a low viscosity index and fairly high sulphur content. On the other hand, lubricating oils, as ordinarily made from parafiin-base crudes of the Pennsylvania type,have a high pour and cloud test, high Conradson carbon content and a Q N fairly high sulphur content, depending on the particular crude source. Oils derived from mixed base crudes may fall somewhere between these limits although usually high in sulphur content.

stituents, is by the use of sulphuric acid. Much stress has recently been put on the danger of overrefining due to the use of this method of refining with its consequent impairment of lubricating value due to over-refinement. Sulphur dioxide has been proposed as a substitute in the refining art but the use of this solvent by itself in refining in viscous fractions, particularly of the paraffintype, has not been, successful from the standpoint of producing a product having the desired high viscosity index, low pourtest and other characteristics. i

I have discovered that by the use of the meth- I ods herein disclosed lubricating oils of any desired viscosity index and scale of purification, coupled with low pour test and low cloud test, can be made from mixed-base or paraffin-base crudes, and the oils so produced are characterized further by low Conradson carbon and low sulphur content. The obtaining of oils having these desired qualities does not depend on methods involving redistillation or acid treatment.

More specifically the invention comprises mixing with a wax-bearing fraction of a mineral oil a solvent mixture comprising two or more solvent liquids of differing solvent properties which, in certain ratios ofone solvent/liquid to other solvent liquids, has substantially complete solvent action on the oil at temperatures of around 100 F., and at temperatures of around 0 F. substantially complete solvent action on the liquid hydrocarbons therein but substantially no solvent action on the solid hydrocarbons therein and of such a nature that uponcooling a solution of the mineral oil fraction in such solvent mixture to 0 F. and removing the solid hydrocarbons so precipitated and the solvent liquid the resulting oil has a cold test of substantially, 0 F. or below but which solvent mixture in certain other ratios of one solvent liquid to the other solvent liquids has, at temperatures of 32 F. and below, a selective solubility asbetween differing viscosity index constituents of hydrocarbon content.

the liquid-- The mixture is then chilled to form a precipitate of solid or semi-solid material comprising suspended wax or solid hydrocarbons which are insoluble in, and immiscible with, the solvent mixture. The mother liquor is separated from the cold mixture advantageously by filtration. The separated mass of solid hydrocarbons is then washed free of mother liquor containing dissolved oil by additional quantities of chilled solvent liquid of approximately the same composition as used in the original mix.

A certain portion of the filtrate from this washing operation may be added to the original filtrate, the amount of liquid so added depending on the amount of dissolved oil contained therein. To the original filtrate or mixture of original filtrate and first wash liquor is then added an additional amount of one of the component solvents of the solvent liquid mixture to alter the percentage composition of the components of the solvent mixture in an amount suflicient to afiect the solvent capacity of the solvent mixture and cause a separation between soluble and insoluble constituents of the hydrocarbons. This mixture is chilled to effect a sharp and rapid separation into two layers, the upper layer containing oils characterized by relatively high viscosity index, and the lower layer containing oils characterized by relatively low viscosity index. The amount and character of the separation is influenced by the amount of alteration in the percentage composition of the components comprising the solvent liquid mixture.

I have found that a suitable solvent liquid mixture may comprise a mixture of liquid sulphur dioxide and an organic solvent liquid such as benzol or one of its homologs, the most common of which are toluol and xylol or a derivative thereof such as monochlorobenzol. Other solvent liquids may also be employed in conjunction with the sulphur dioxide, as for example, propylene dichloride. The selective solvent action of a mixture of these solvents upon the various constituents of a hydrocarbon oil fraction is readily altered by varying the proportion of the solvent components of the mixture.

As an example in carrying out the above invention:

About 200 gallons of untreated vacuum distilled wax distillate having a viscosity of 70 Saybolt Universal seconds at 210 F. with a pour test of 80 F. and a sulphur content of about .4%, derived from a semi-paraffin base crude, is mixed with 600 gallons of a solvent liquid comprising 30% sulphur dioxide and 70% monochlorobenzol, the mixture is chilled to -15 F. to precipitate the wax-like or solid hydrocarbons and introduced to filtering means described in my copending application, Serial No. 585,844, for Method of and apparatus for filtration, filed January 11, 1932, now matured into U. S. Patent 2,003,664, wherein the solid hydrocarbons are separated from the liquid to produce a filter cake.

A Wash solvent liquid comprising 30% sulphur dioxide and 70% monochlorobenzol and chilled to 15 F. is introduced to the press to wash out of the filter cake the adhering mother liquor. The first portion of the filtrate resulting from this washing, which may contain a substantial quantity of dissolved oil may be mixed with the original filtrate, while the remaining portion may be used to mix with and dissolve fresh untreated wax distillate to be treated in the same manner as the original material as above described.

The slurry remaining in the filter press is then removed and the bulk of the adhering solvent filtered ofi advantageously by filtering this slurry in a filter means such, for example, as described in my co-pending application, Serial No. 588,586, for Filtration, filed January 25, 1932, now matured into U. S. Patent 1,920,126. The solvent retained in the resulting filter cake is evaporated from the wax and the wax contacted with clay or finished up in the usual manner.

The wax in the above example will amount to approximately seven and one-half per cent of the original Wax distillate and after removal of the solvent by evaporation and decolorizing will be White and have a melting point, without sweating, of about 136 F.

To the mixture of original filtrate and initial portion of wash liquor is added liquid sulphur dioxide chilled to a temerature of -10 F. This additional sulphur dioxide should bring the ratio of sulphur dioxide to monochlorobenzol up to about equal volumes of each.

The mixture is well stirred and allowed to settle and stratify. The top layer will comprise low gravity, relatively high viscosity index oils, while the lower layer comprises high gravity, low viscosity index oils. The oil in the top layer after removal of the solvent will have a gravity of approximately 27.5 A. P. I., a viscosity of 66 Saybolt Universal seconds at 210 F. and a viscosity index of approximately 87. The oil in the bottom layer, after removal of the solvent, will have a gravity of approximately 13 A. P. 1., a viscosity of approximately 118 Salbolt Universal seconds at 210 F. and a viscosity index below 30.

The fraction of relatively high viscosity oil may be contacted with clay and filtered, and is then ready for use as a so-called wide cut, or it may be fractionated by vacuum distillation to produce cuts of narrower distillation range.

On the other hand, this relatively high viscosity material may be still further improved or refined by dissolving in monochlorobenzol, cooling the mixture to 0 F. and adding chilled liquid sulphur dioxide in about the same proportion as the monochlorobenzol. The mixture is well stirred, chilled to l0 F. and allowed to settle. The oil in the top layer, after removal of the solvent, contacting and steaming in the presence of clay and contact filtering, will have the following approximate characteristics: Gravity 30.6, viscosity of 64 Salbolt Universal seconds at 210 F., viscosity index 95, Conradson carbon .015, and sulphur .1, with a pour test of 5 F.

As an additional example in carrying out the above invention:

Untreated vacuum distilled wax distillate, similar to that used in the preceding example, is also similarly mixed with sulphur dioxide and monochlorobenzol, in the proportion of about 200 gallons of oil to 600 gallons solvent mixture and chilled to 15 F. to precipitate the wax-like or solid hydrocarbons. The mixture is filtered and the reslting filter cake washed with the same fresh solvent in the same manner, the initial portion of the wash filtrate being mixed With the original filtrate.

To this mixture of original filtrate and wash liquor is added chilled sulphur dioxide sufficient to give a solvent mixture of 60% sulphur dioxide and 401% monochlorobenzol. The mixture is stirred well, chilled to -l0 F. and allowed to settle and stratify.

The separated bottom layer is drawn oil, the solvent evaporated and the oil recovered. There will be recovered an oil having a gravity of approximately 12.4 A. P. I. and a viscosity index of approximately -32.

The separated top layer is mixed with a chilled mixture of monochlorobenzol and sulphur dioxide comprising about 40% sulphur dioxide and 60% monochlorobenzol, well stirred, chilled to 10 F. and allowed to separate. The bottom layer is drawn oif, the solventevaporated and the contained oil contacted at 500 F. with 20 pounds of clay. to the barrel. This contacting may be carried out in the presence of steam. The oil and clay mixture is cooled to 350 F. and filtered. The filtered oil will amount to about 73 gallons and have the following approximate characteristicst Gravity 27.5 A. P. I., viscosity 67 Saybolt Universal seconds at 210 F., viscosity index 79 with a pour test of 10 F.

The solvent is evaporated from the separated top layer and the contained oil contacted at 500 F. with 20 pounds of clay to the barrel while steaming. The oil and clay mixture is cooled to 350 F. and filtered. The filtered oil will have the following approximate characteristics: Gravity 31.1 A. P. I., viscosity 63 Saybolt Universal seconds at 210 F., viscosity index 102, pour test 5 F., Conradson carbon .012, sulphur .09.

When using propylene dichloride as one of the solvent components, the procedure is substantially similar to that outlined in the'foregoing examples except that the proportions of propylene dichloride and sulphur dioxide to each other and to the oil undergoing treatment may differ considerably. Thus, in the initial treating step for the removal of wax constituents, the wax-bearing oil may be mixed with. straight propylene dichloride alone or with a solvent mixture comprising this solvent liquid and not in excess of about l /2% by volume of sulphur dioxide. .The resulting cold solution of liquid hydrocarbons in solvent liquid isthen mixed with fresh cold sulphur dioxide in an amount, for example, which may be equal to. or greater than the propylene dichloride content but usually in excess of about 20% of the solvent mix. This mixture is then chilled to 5 F. or below and settled to form two layers from which the oilis recovered and finished up as has already been described.

The solvent is advantageously removed from the separated oil by evaporation and, in the case of the high-boiling solvent component, under diminished pressure. The evaporation may be carried out in the presence of steam and the claycontacting material may be added toor commingled with the oil during the latterstage of the solvent removal. I have found that when the clay contacting is carried out in the presence of a small amount of sulphur dioxide, the final prod not is improved in color.

When using propylene dichloride and sulphur dioxide, as above described, products are obtained having the following characteristics:

The invention is not limited to the production of final products having the particular characteristics of those described above. Products of differing characteristics, as desired, may be prepared loy varying the proportions of the solvent liquids an'dalso the temperatures at which the treating steps are carried out. l.

Furthermore, the invention is notlimitedto the treatment of wax distillate such as given in the examples herein but is adapted to the treatment of other paraflin-containing fractions, precipitates or materials somewhat similar in nature derived in various ways from mineral oils.

with my'invention, final products of desired char acteristics can be obtained.

The invention is not restricted to any particular operating conditions such as that of temperature, or the composition of the solvent mixtures employed since these conditions may advantageously be varied, depending upon the nature of the fraction undergoing treatment as Well as upon the particular characteristics desired in the final product.

It is also contemplated, in many instances, that it may be of advantage to carry on the filtration step in the presence of a comminuted solid filter-aid material. mixed with the chilled mixture of oil and solvent liquid prior to introduction to the filtering means.

In order to illustrate further the operation of the process of my invention reference may be made to the flow diagram shown in the accompanying drawing. g

The wax-bearing oil to betreated is drawn from a source not shown and introduced to a mixer I wherein it is mixed with solvent also conducted from a source not shown. As indicated, the solvent comprises a mixture of sulphur dioxide and a modifying solvent consisting of monochlorbenzol.

vThe oil and solvent liquids are mixed in the proper proportion so that upon chilling wax constituents of the oil are precipitated. The resulting mixture is then passed to a chiller 2 wherein. it is chilled to the desired dewaxing temperature as, for example, around minus 15 F.

The chilled mixture is then passed to a filter 3 wherein the precipitated solid hydrocarbons are removed in the form of a filter cake, producing a dewaxed filtrate. The filter cake is advantageously washed in situ by introducing to the filter wash solvent liquid. from a chiller 4.

The washed filter cake is discharged from the filter to a receiver 5. Where the washed wax is in the form of a slurry it is passed from the receiver 5.to a filter 6, as previously described, for the purpose of removing retained liquid.

From the filter 6 the wax is conducted to a still 1 wherein any remaining solvent liquid may be removed. The wax is withdrawn from the still and passed to'a receiver 8, following which it may be subjected to'further treatment, such as decolorization.

The main body of .filtrate liquid comprising dewaxed oil is passed fromthe filter 3 to a fil- Such material may be adan additional quantity of sulphur dioxide introduced from a chiller l2.

Sufficient sulphur dioxide is thus added so as to increase the ratio of sulphur dioxide to modifying solvent and thereby cause separation into liquid phases upon settling. The modified mixture is passed from the mixer to a settler l3 wherein separation into liquid phases, i. e., extract and rafiinate phases, occurs.

The extract phase is drawn off to a receiver l4, while the raffinate phase is drawn off to a receiver l5.

The extract phase is conducted to a still [6 wherein the solvent liquid is removed from the oil and the remaining extract oil is withdrawn to a receiver IT.

The raffinate phase is drawn off from the receiver [5 to a still l8 wherein the solvent liquid is removed. The raflinate oil thus produced is drawn 01f from the still I8 to a receiver I9.

The extract and rafiinate oil thus produced is then subjected to such further treatment as may be desired.

Obviously many modifications and variations of the invention, as hereinbefore set forth, may be made without departing from the spirit and scope thereof, and therefore only such limitations should be imposed as are indicated in the appended claims.

I claim:

1. In the manufacture of lubricating oils of desired high .viscosity index from mineral oil containing constituents of relatively high and relatively low viscosity index, the method of fractionally separating the oil into fractions of differing viscosity index comprising extracting the oil with liquid sulphur dioxide in the presence of a chlorinated aliphatic hydrocarbon solvent liquid having substantially less selective action than liquid sulphur dioxide as between said relatively high and relatively low viscosity index constituents and in proportions sufiicientto effect the desired degree of selective solvent action upon the oil undergoing treatment.

2. Inthe process of manufacturing high viscosity index lubricating oil having a low pour test from wax-bearing mineral oil, the method which comprises mixing with the oil a solvent liquid mixture composed of an extraction solvent having a selective solvent action substantially of the character of liquid sulphur dioxide as between constituents of the oil of differing viscosity indices, and having anti-solvent properties for wax at temperatures of 0 F. and below, and a modifying solvent liquid of relatively less selective action mixed with each other and with the oil in proportions such that the mixture has substantially complete solvent action on the liquid hydrocarbon constituents and substantially no solvent action on the solid hydrocarbon constituents of the oil at temperatures of around 0 F., chilling the mixture to 0 F. and below to precipitate the solid hydrocarbons, removing the solid hydrocarbons thus precipitated, increasing the proportion of extraction solvent component in the dewaxed mixture, separating the mixture while maintained at a temperature of around 0 F. and below into a solvent phase containing low viscosity index constituents of the oil dissolved in the solvent, and an oil phase comprising relatively high viscosity index constituents of the oil, and separating the two phases.

3. A process of dewaxing and fractionating a wax-bearing oil into fractions relatively paraffinic and naphthenic with respect to the original oil which comprises dissolving the oil in a selective solvent adapted to precipitate therefrom at least a substantial portion of the wax contained therein, precipitating said wax, removing said wax, modifying the dewaxed solution to cause the formation of two liquid phases therefrom, each of said phases containing a portion of the oil and a portion of the solvent, separating said two phases, and recovering oil and solvent from each of said phases.

4. A process of dewaxing and fractionating a wax-bearing oil into fractions relatively paraffinic and naphthenic with respect to the original oil which comprises mixing the oil with a selective solvent adapted to precipitate therefrom at least a substantial portion of the wax contained therein, precipitating said wax, removing said wax, modifying the composition of the solvent in the dewaxed solution to cause the formation of two liquid phases therefrom, each of said phases containing a portion of the oil and a portion of the solvent, separating said I two phases, and recovering the oil and solvent from each of said phases.

5. A process of dewaxing and fractionating a wax-bearing oil into fractions relatively paraffinic and naphthenic with respect to the original oil which comprises mixing the oil with a selective solvent adapted to precipitate therefrom at least a substantial portion of the wax contained therein, precipitating said wax, removing said wax, adding to the dewaxed solution a solvent having high solvent power for relatively naphthenic constituents thereby to modify the dewaxed solution and cause the formation of two liquid phases, each of said phases containing a portion of the oil and a portion of the solvent, separating said two phases, and recovering the oil and solvent from each of said phases.

6. A process of dewaxing and fractionating a wax-bearing oil into fractions relatively paraffinic and naphthenic with respect to the original oil which comprises mixing the oil with a selective solvent comprising a mixture of sulphur dioxide and a modifying solvent relatively less selective than sulphur dioxide as between naphthenic and parafiinic constituents, adapted to precipitate therefrom at least a substantial portion of. the wax contained therein, precipitating said wax, removing said wax, modifying the dewaxed solution to cause the formation of two liquid phases therefrom, each of said phases containing a portion of the oil and a portion of the solvent, separating said two phases, and recovering oil and solvent from each of said phases.

7. A method of dewaxing wax-bearing mineral lubricating oil for the production of oil having a pour test of 0 F. and below, which comprises dissolving the wax-bearing oil ina solvent mixture comprising liquid sulphur dioxide and a modifying solvent having relatively less selective action than sulphur dioxide as between the solid hydrocarbon and liquid hydrocarbon constituents of the oil containing less than 50% sulphur dioxide, and in proportions such that at temperatures of 0 F. and below the mixture has substantially complete solvent action on the liquid hydrocarbon constituents and substantially no solvent action on the solid hydrocarbon constituents of the oil, chilling the mixture to a temperature of 0 F. and below to precipitate the solid hydrocarbon constituents, and separating the thus precipitated solid hydrocarbon constituents from the cold mixture.

8. In the manufacture of mineral lubricating oil, the method which comprises mixing waxsulphur dioxide and a modifying solvent having relatively less selective. action as between low and high viscosity index constituents in proportions such that the mixture has selective action as between Wax and oil at temperatures of around 0 F., chilling the mixture to precipitate wax, removing the wax thus precipitated to produce a dewaxed mixture of oil and solvent, modifying the solvent composition of the dewaxed mixture, separating the mixture into an extract phase containing low viscosity index constituents of the oil, and a raffinate phase containing high viscosity index constituents of the oil, and separating the two phases.

9. A process of solvent refining wax-bearing mineral oil in which the oil is first dewaxed and then separated into fractions relatively paraffinic and naphthenic with respect to the original oil, which comprises mixing the oil with a selective solvent liquid mixture adapted to precipitate at least a substantial portion of the wax, chilling the mixture to precipitate wax, removing the wax thus precipitated from the mixture of solvent and oil comprising the naphthenic and paraflinic liquid constituents of the oil to produce a dewaxed mixture, modifying the composition of the solvent in the dewaxed mixture to cause the formation of extract and railinate phases, the extract phase containing mainly naphthenic constituents and the rafiinate phase containing mainly parafiinic constituents, and separating the two phases.

10. A method of dewaxing wax-bearing mineral lubricating oil for the production of oil having a pour test of 0 F. and below, which comprises mixing the wax-bearing oil with a solvent mixture comprising liquid sulphur dioxide and a modifying solvent having relatively less selective action than sulphur dioxide as between the solid hydrocarbon and liquid hydrocarbon constituents of the oil, containing less than 50% sulphur dioxide, and in proportions such that at temperatures of 0 F. and below the mixture has substantially complete solvent action on the liquid hydrocarbon constituents and substantially no solvent action on the solid hydrocarbon constituents of the oil, chilling the mixture to a temperature of 0 F. and below to precipitate the solid hydrocarbon constituents,

and separating the thus precipitated solid hydrocarbon constituents from the cold mixture.

11. The method according to claim in which the modifying solvent comprises a dichlorinated aliphatic hydrocarbon of the type such as propylene dichloride.

12. The method according to claim 10 in which the modifying solvent comprises an aromatic hydrocarbon of the class consisting of benzol and its homologs.

13. The method according to claim 10 in which the modifying solvent comprises a monochlorinated monocyclic aromatic hydrocarbon of the type such as monochlorbenzol.

14. The process of dewaxing a wax-bearing mineral lubricating oil which comprises diluting the wax-bearing oil with a greater volume of a solvent mixture essentially comprised of a solvent of the class consisting of benzol and its homologs in greater proportion and liquid sulphur dioxide in lesser proportion, the volumes and proportions being such that at low dewaxing temperatures the mixture has substantially action onthe solid hydrocarbon constituents of the oil, chilling the mixture to atemperature inthe neighborhood of 0 F. or less to precipitate the solid hydrocarbon constituents, and sepe ,arating the thus precipitated solid hydrocarbon constituentsfrom the cold mixture.

15. In the process of making a low cold test high viscosity index lubricating oil from wax bearing mineral oil, the steps which consist in dissolving the wax bearing oil in a solvent consisting essentially of sulphur dioxide and monochlorbenzol, chilling the solution to effect precipitation of paraffin wax, filtering out the precipitated wax, adding further sulphur dioxide to the filtrate, and effecting a Stratification and separation of the oil content into relatively high viscosity index oil and relatively low'viscosity index oil.

. 16. The process of making a low cold test high viscosity index lubricating oil from wax bearing mineral oil, which comprises dissolving the wax bearing oil in a solvent consisting essentially of sulphur dioxide and a modifying solvent comprising a mono-chlorinated mono-cyclic aromatic hydrocarbon of the character of monochlorbenzol, chilling the solution to effect separation of paraffin wax, removing the wax thus separated, increasing the proportion of sulphur .dioxide to modifying solvent in the dewaxed mixture such that the solvent has selective action as between constituents of the oil of differcient to effect the desired degree of selective solvent action upon the oil undergoing treatment. 18.v The method of manufacturing lubricating oil of high viscosity index from mineral oil containing constituents of relatively high and relatively low viscosity index comprising extracting the oil with liquid sulphur dioxide in the presence of-monochlorbenzol in proportions sufficient to effect the desired degree of selective solvent action upon the oil, separating from the mixture a fraction composed of relatively high viscosity index constituents, and contacting the separated oil with solid adsorbent material to produce a neutral finished product of desired high viscosity index.

19. The process of making a low cold test high viscosity index lubricating oil from wax bearing mineral oil, which comprises dissolving the wax bearing oil in a solvent consisting essentially of sulphur dioxide and a modifying solvent comprising a mono-chlorinated mono-cyclic aromatic hydrocarbon of the character of monochlorbenzol, chilling the solution to effect separation of paraiiln wax, removing the Wax thus separated,

increasing the proportion of sulphur dioxide to modifying solvent in the dewaxed mixture such that the solvent has selective action as between constituents of the oil of differing viscosity indices, separating from the resulting dewaxed oil a fraction of desired. low pour test and high viscosity index and contacting the thus separated oil with solid adsorbent material to produce a neutralafinished product of desired low pour test and high viscosity index.

-.' 20; Thepro'cess of manufacturing low cold test high viscosity index lubricating oil from wax bearing mineral oil which comprises dissolving the wax bearing oil in a solvent mixture composed of sulphur dioxide and benzol containing less than 50% sulphur dioxide, and mixed with each other and with the oil in a proportion substantially to yield an oil of zero pour test when the mixture is dewaxed at about F., chilling the mixture to separate the wax, removing the wax thus separated, increasing the proportion of sulphur dioxide to benzol in the dewaxed mixture such that the solvent has selective action as betwe'enconstituents of the oil of differing viscosity indices', separating from the resulting dewaxed oil a fraction of desired low pour test and high viscosity index, and recovering the solvent from the-dewaxed and separated oil.

" 21. In the manufacture of mineral lubricating oil, the method which comprises mixing wax bearing mineral oil containing low and high viscosity index constituents with sulphur dioxide and a modifying solvent having relatively less selective action as between low and high viscosity index constituents, the sulphur dioxide comprising less than 50% of the solvent mixture, chilling the mixture to precipitate wax, removing the wax thus precipitated to produce a dewaxed mixture of; oil :andsolvent, increasing the ratio of sulphur dioxide to, modifying solvent in the dewaxed mixture to render the solvent mixture selective as between low and high viscosity index constituents of the oil, separating the mixture into an extract phase containing low viscosity index constituents of the oil, and a rafiinate phase containing high viscosity index constituents of the oil, and separating'the two phases.

22. A method of dewaxing wax-bearing mineral lubricating oil for the production of oil having a low pour test, which comprises mixing with the wax-bearing oil at least an equal volume of a mixture of liquid sulphur dioxide and monochlorbenzol in which the sulphur dioxide is about 30%, chilling the mixture to precipitate wax, and separating the wax.

23. A method of dewaxing wax-bearing mineral lubricating oil for the production of oil having a low pour test, which comprises mixing with the wax-bearing oil at least an equal volume of a solvent mixture of liquid sulphur dioxide and modifying solventhaving relatively less selective action than sulphur dioxide as between the solid hydrocarbon and liquid hydrocarbon constituents of the oil, and in which solvent mixture the sulphur dioxide is about 30%, chilling the mixture to precipitate wax, and separating the wax.

FRANCIS X. GOVERS. 

